The general problem with which we are concerned is the elucidation of cellular mechanisms of gene regulation which are related to the neoplastic process in humans. The phenomenon of ectopic protein synthesis in human cancer offers a good experimental model for investigating this problem. The ectopic synthesis of proteins by non-trophoblastic neoplasms is of special interest because of the frequent association of similar characteristics in neoplastic cells and embryonic cells. This has suggested that there may be a link between the mechanisms associated with the de-repression of the genes synthesizing embryonic proteins and those involved in neoplastic transformation. We are conducting experiments in two fundamental categories: (1) Studies on the regulation of gene expression in normal and neoplastic cells: In these studies we measure and compare patterns of synthesis of placental proteins and their corresponding specific messengers in normal trophoblast, in choriocarcinoma, and in nontrophoblastic tumors to determine whether similar regulatory mechanisms are operant. These experiments are performed using tissue cultures derived from trophoblasts and from tumors which synthesize placental proteins ectopically. (2) Studies on the structure, function and tissue distribution of trophoblastic plasma membrane glycoproteins: These studies are a continuation of the characterization of glycoproteins expressed on the brush border membrane of the term placenta. We will determine the distribution of these proteins among various normal adult tissues and a variety of tumor tissues. Furthermore, we will attempt to identify specific functions with individual glycoproteins components and study their topographical distribution on cells in different physiological states.